Cylinder plating rack

ABSTRACT

A plating and stripping rack for chromium electroplating and stripping the interior of hollow, substantially cylindrical objects in a plating bath through the action of electrical current, the rack including a support frame, an anode insulated from the frame but supported thereby, a cathode supported and insulated from the anode along the frame and a cylindrical nonsimilar, non-consumed metal insert for critical placement within the hollow cylindrical object to be plated or stripped and connected to the anode.

[ June 10, 1975 United States Patent [191 Wallace 3,297,559 1/1967 Farrow...................W....t...204/242 CYLINDER PLATING RACK [76] Inventor:

Bruce Evans Wallace, 1819 Robinhood Rd, Winston-Salem, f NC 27104 Assistant Examiner-D. R. Valentine [22] Filed:

[57] ABSTRACT A plating and stripping rack for chromium electroplating and stripping the interior of hollow, substantially cylindrical objects in a plating bath through the action June 4, 1973 Appl. No.: 366,420

[52] US. 204/272; 204/286; 204/297 R [51] Int. (1mm Bolk 3/00; Czzd 1/02;C23b 5/70 of electrlcal current, the rack including a support 58 Field of Search......... 204/242 286,297 R, 272 frame anode insulated from the frame but P- ported thereby, a cathode supported and insulated [56] References Cited from the anode along the frame and a cylindrical non- UNITED STATES PATENTS similar, non-consumed metal insert for critical placement within the hollow cylindrical object to be plated or stripped and connected to the anode.

204/272 204/272 X 204/297 W X Werrett.................. Boguski 2 Claims, 8 Drawing Figures PATENTEDJuHmms 3888755 20 T ul .m' .m I -E INSULATING O T l I PLATE 0 1 I 28 l O 28 l l :l l l- 30 2e 40/ :1 PM h 40 A {I II .I 4 INSULATING J 28 PLATE SHEET PATENTEDJUH 10 ms r FIG.7

FIGS

FIG.6

CYLINDER PLATING RACK BACKGROUND, BRIEF SUMMARY AND OBJECTIVES OF THE INVENTION The present invention relates to the art of producing metallic coatings through the action of electric current and is particularly directed to devices for chromium electroplating and stripping the hollow interiors of cylindrical objects.

Electroplating, the art of producing metallic coatings through the action of electric current, provides metal with numerous important characteristics including improved appearance, corrosion resistance, hardness, bearing qualities or some of the properties of the basis metal on which the coating is produced. The essential parts of a typical electroplating system are the plating bath which contains an aqueous solution of the metal to be deposited, a source of direct current electricity, the object to be coated, and a sheet or bar of the plating metal. When the negative terminal of the direct current source (the cathode) is connected to the object and the positive terminal (the anode) is in contact with the plating solution, metal ions migrate to the cathode surface transforming them to the metallic state and attaching them to that surface.

Electroplating chemistry has been known for many, many years. The general practice in electroplating any particular object is to construct a plating rack or holding device that will suspend the object to be plated in the plating bath in a manner to preclude any irregular deposition of metallic particles on the article surface.

The rack must be designed critically to ensure uniformity in coating.

It is also customary to provide a stripping rack which makes it possible to clean the object to be plated by reversing the electrical connections and hence the plating process. The stripping rack in many instances is the same structure as the plating rack.

' Certain objects lend themselves readily to electroplating, particularly when the metallic coating is to be deposited on an exterior surface of the object. Other objects because of their peculiar and particular shape present more difficult problems.

An especially difficult item to electroplate in the past has been the interior walls of extended lengths of hollow cylinders with chromium because the positioning of the anode within the interior of a cylinder has not been determined by experiment. Furthermore, a functionally satisfactory plating rack for interior cylinder plating has not been available. In specific installations such as boiler walls and the like, the chromium coated cylinder. interior walls must be consistent in thickness and in surface composition in order to provide an efficient and durable component.

The present invention is directed to a plating and stripping rack specifically designed for the chromium electroplating of cylinder interior Walls. The invention includes two complementary sections for maintaining the anode and cathode each of which are comprised of two wing-shaped members secured to an insulating plate. A cylindrical insert connects to the anode and is suitably positioned within the interior of the cylinder to provide uniform distances between anode and cathode for the electroplating process. The insert is preferably made of lead but in any event of a composition different from that of the element to be plated, and further rigidity of the unit is brought about by connecting the upper insulating plate carrying the wing-shaped members in a fixed relationship to another lower insulating plate by a plurality of spacing rods. The resulting device ensures a stable, suspensionable device for introducing the cylinder into the plating bath.

The rack, with certain minor changes, can be used as a stripping rack to clean interior cylinder walls or to strip previously but imperfectly plated articles prior to again initiating the plating operation.

From the foregoing it will be apparent that a principal object of the present invention is the provision of a plating and stripping rack for electroplating and/or cleaning cylindrically-shaped objects.

Another objective of the present invention is to provide a specific plating and stripping rack for the electroplating and cleaning of interior cylindrical walls in a plating bath.

Yet another object of the present invention is to provide a plating and stripping rack which is stable in construction sufficient to maintain rather precise dimensions between the anode and cathode during the plating process.

A further object of the present invention is to provide a plating and stripping rack of the type described which is relatively simple in construction and reliable in use.

These and other objectives of the present invention will become more apparent after consideration of the following detailed description taken in conjunction with the accompanying drawings wherein like charac ters of reference designate like parts throughout the several views.

FIGURE DESCRIPTION FIG. 1 is a perspective view of one embodiment of a plating and stripping rack comprising the present invention supported in a manner that permits it to be suspended within a plating bath while carrying a cylinder to be plated interiorally.

FIG. 2 is a front elevational, sectional view of the plating and stripping rack illustrated in FIG. 1.

FIG. 3 is a plan view of the plating and stripping rack illustrated in FIGS. 1 and 2.

FIG. 4 is an end elevational and sectional view of the plating and stripping rack shown in FIGS. 1, 2 and 3.

FIG. 5 is a perspective view of a second embodiment of a plating and stripping rack comprising the present invention supported in a manner that permits it to be suspended within a plating bath while carrying a cylinder to be plated interiorally.

FIG. 6 is a front elevational, sectional view of the plating and stripping rack illustrated in FIG. 5.

FIG. 7 is a plan view of the plating and stripping rack illustrated in FIGS. 5 and 6.

FIG. 8 is an end elevational and sectional view of the plating and stripping rack shown in FIGS. 1, 2 and 3.

DETAILED DESCRIPTION OF THE DISCLOSURE Referring now to the drawings and particularly to FIG. 2, a support frame, shown generally as 10, having two complementary sections 12, both of which are bolted to an upper insulating plate 14 in the manner shown. Each of the complementary sections 12 is comprised of two wing-shaped members 16. The support frame 10 is carried at one end 18 by a support rod 20 which also serves as the cathode connecting to the DC power supply (not shown) and at the other end 22 by support rod 24 also serving as the anode of the system. Any convenient sustaining means (such as suggested in dotted lines in FIG. 1) may be used to support the entire assembly for immersion in a plating bath.

Electrical connectors in the form of a copper strip or bus bar 26 extend from anode 24 by being secured thereagainst as shown in FIG. 2. Two conductors join anode 24 for a connection to other components of the unit which will subsequently be described.

Copper strip 26 also extends from cathode 20 downwardly to a plurality of clamps 28 designed to encompass contiguously the exterior of a cylindrical object shown in hidden lines as 30 (FIG. 2). Two such clamps are used in the present preferred embodiment, however obviously these may be varied as the need arises for more critical plated thicknesses.

A cylindrical insert 32 connects to the two conductors 26 of anode 22, one conductor being secured to the top 34 of insert 32 while the second conductor is fastened to the bottom 36 of that same member. The dual connections are provided in order to give uniform current density throughout the interior of cylinder 30 during the electroplating process. Additional rigidity is provided the invention by including a lower insulating plate 38 and connecting that plate to upper insulating plate 14 by four spacing rods 40.

An alternative and somewhat simplified emobodiment of the plating and stripping rack comprising the present invention is illustrated in FIGS. through 8 wherein a support frame, shown generally as 42 includes two complementary sections 44 similar to the embodiment described previously. The basic difference in the alternative embodiment is that only one contiguously encircling clamp 46 is extended from the cathode 48 thus providing a somewhat simplified unit.

In actual practice, it has been found that the embodiment illustrated in FIGS. 1 through 4 is best suited for the electroplating procedure while the embodiment reflected in FIGS. 5 through 8 is best adapted to strip and clean cylindrical walls prior to the electroplating process. While good results have been obtained by using the suggested embodiments for the specified processes, obviously either embodiment willresult in satisfactory electroplating and cleaning depending upon the particular situation.

In using the present invention to electroplate with chromium cylindrical walls of up to say 38 to 40 inches in length, a plating bath solution of chromic acid (approximately 33 ounces per gallon) and sulfuric acid (approximately 0.33 ounces per gallon) is maintained at a temperature of approximately 133 F. Current density for chromium, plating in this solution is approximately 2 amps per square inch. To achieve a plating thickness of from 0.8 mil to 1.2 mils per hour it is critical that, the anode to cathode distance, i.e., the distance x from insert 32s exterior surface to the interior surface of cylinder 30, must be not less than 1 or more than 2 inches in order to achieve satisfactory results. Obviously other inserts (32 or brackets 28) can be used to maintain the critical distance between anodefand cathode when cylinders of differing external and internal diameters are plated. 1 r a While insert 32 might be of any substance except that being plated, it has been found more desirable to have this component formed from lead or from a composition of approximately 92% lead with 8% tin. T hese substances have a tendency to last considerably longer than conventional metals during the electroplating process. vi

While the present invention finds special application in chromium plating interior cylinder walls, obvious-1y other metallic coverings may be applied using the same apparatus with satisfactory results. While many modifications may be made in the support frame, anode, cathode and insert as well as other elements may be made without departing from the spirit andvscope of the described primary embodiment, it is to be understood that the present invention is notlimited by any specific illustrations or examples excep t to the extent defined in the following claims.

I claim:

l. A plating and stripping rack for electroplating and cleaning the interior of hollow substantially cylindrical objects in a plating bath comprising: a support frame having two complementary sections, each of said sections having two winged members; an anode formed by one of said complementary frame sections; 'a cathode formed by the other of said complementary frame sections and positioned a fixed preselected distance from said anode by said frame; and a cylindricalinsert having first and second ends and being of a composition dissimilar to the cylindrical object being plated for placement within the hollow cylindrical object affixed to said anode ends and forming at part thereof, said cathode having clamping means for securing the object to be plated, said frame including insulating means separating and maintaining saidflanode and cathode, and said insulating means including an upper' and lower insulating plate maintaining said anode and said cathode in a fixed relationship each with the other.

2. The rack as claimed in claim 1 wherein said anode and said cathode are always fixedly supported a distance of no less than one and no greater than 2 inches from each other. 

1. A plating and stripping rack for electroplating and cleaning the interior of hollow substantially cylindrical objects in a plating bath comprising: a support frame having two complementary sections, each of saId sections having two winged - members; an anode formed by one of said complementary frame sections; a cathode formed by the other of said complementary frame sections and positioned a fixed preselected distance from said anode by said frame; and a cylindrical insert having first and second ends and being of a composition dissimilar to the cylindrical object being plated for placement within the hollow cylindrical object affixed to said anode ends and forming a part thereof, said cathode having clamping means for securing the object to be plated, said frame including insulating means separating and maintaining said anode and cathode, and said insulating means including an upper and lower insulating plate maintaining said anode and said cathode in a fixed relationship each with the other.
 2. The rack as claimed in claim 1 wherein said anode and said cathode are always fixedly supported a distance of no less than one and no greater than 2 inches from each other. 